As a light emitting material used in a light emitting layer of a light emitting device, a composition prepared by doping a host material with a phosphorescent compound showing light emission from a triplet excited state is known.
It is important that the lowest triplet excited state (hereinafter, referred to also as “T1”) is at high energy level for realizing high light emission efficiency as the basic property of the above-described host material.
It is known that a polymer compound such as polyvinylcarbazole and the like can be suitably used as the above-described host material since an organic film can be formed with such a compound by a coating method (Patent document 1).
A polymer compound containing as a repeating unit a 1,4-phenylene group having specific substituents at 2-position and 5-position (Patent document 1) and a polymer compound containing as a repeating unit a fluorene-2,7-diyl group and a 1,4-phenylene group having specific substituents at 2-position and 5-position (Patent document 2) are known as the above-described host material.